The science behind magnetic materials for technological applications
Magnets are used in various technological applications, e.g. computers, MRI scanners and mobile phones. All materials are magnetic, some more than others. Controlling magnetic anisotropy - the directional dependence of a material's magnetic properties – is essential for understanding the fundamentals of magnetism. A team of researchers from HFML-FELIX and the Institute of Molecules and Materials (IMM) have worked closely together to address the quest of molecular magnetic anisotropy experimentally. The outcomes are relevant for the fundamental understanding of magnetic anisotropy, and can be useful in the design of materials for technological applications. The results are published in the open access journal Physical Review Research.
When a material is exposed to a high magnetic field, it is usually magnetized simply along the field, no matter in which direction it is applied. But some materials are easier or harder to magnetize, depending on the direction of the external magnetic field. These materials are called magnetically anisotropic. They show a direction-dependent energy with minima in certain directions (easy axes) and maxima in others (hard axes). This cannot be explained by just one thing, it is rather a sum of several factors. For this reason, controlling this magnetic anisotropy is a real quest. At the same time, it is a key requirement for the fundamental understanding of molecular magnetism and is a prerequisite for numerous applications in magnetic storage, spintronics, and all-spin logic devices.
Design, measure and understand materials
An interdisciplinary team of researchers was able to reveal the fundamental science behind magnetic anisotropy. They also demonstrated that it is possible to control and switch magnetic anisotropy on a molecular level. Professor Uli Zeitler, Semiconductors and Nanostructures at HFML-FELIX, explains the importance of this team performance: “We have been able to bundle all the expertise for this very complex experiment. Indeed, it combines the ability to design, measure and understand materials, one of the core objectives of the IMM.” Professor Gerrit Groenenboom, Theoretical and Computational Chemistry at the IMM, adds: "The experimental data reflects the quantum mechanical properties of individual ions and the interpretation provides a great challenge to theoretical chemists."
Chemical structure of the Mn4 cluster investigated. The four magnetic Mn(II) ions engage in an exchange interaction (yellow lines) mediated by the surrounding atoms which leads to a complex magnetic molecule.
The experiment is based on the knowledge of several research groups. Laurens Peters, PhD student Soft Condensed Matter & Nanomaterials at HFML-FELIX and the Molecular Materials cluster of the IMM, synthesized a spin system with four antiferromagnetically coupled manganese ions. Paul Tinnemans, Research Assistant Solid State Chemistry, determined its crystal structure. Gerrit Groenenboom provided the necessary theoretical background and calculations. The magnetization experiments were then performed by PhD’s Erik Kampert and Laurens Peters under the supervision of Professor Peter Christianen, Assistant Professor Hans Engelkamp (both Soft Condensed Matter & Nanomaterials, HFML-FELIX) and Uli Zeitler. To be able to perform the experiment, researchers and technicians of HFML-FELIX designed and home-built a magnetometer, able to work in extremely high magnetic fields (up to 33 Tesla) and temperatures as low as -273 degrees Celsius.
Paul Tinnemans, Hans Engelkamp and Uli Zeitler at HFML-FELIX
Although the study is fundamentally orientated, the gained knowledge is promising for numerous applications in magnetic storage, spintronics, and all-spin logic devices. Hans Engelkamp: “Thorough understanding of the design rules for this type of materials might enable the design and production of single molecule magnets, which can be used for extremely high-density information storage.”
HMFL-FELIX and IMM
At HFML-FELIX, high magnetic fields and intense (far) infrared free electron lasers are designed and used to investigate the properties and functionality of molecules and materials, realize fundamental scientific breakthroughs and tackle societal challenges in the areas of Health, Energy and Smart Materials. HFML-FELIX is scientifically embedded in the Institute for Molecules and Materials (IMM) at Radboud University. (Bio)chemists, physicists, theorists and experimentalists, work closely together to unravel and control the functioning of molecules and materials at the smallest length and time scales.
Magnetic anisotropy of individually addressed spin states, L. C. J. M. Peters, P. C. M. Christianen, H. Engelkamp, G. C. Groenenboom, J. C. Maan, E. Kampert, P. T. Tinnemans, A. E. Rowan and U. Zeitler, Phys. Rev. Research 3, L042042 (2021)
Uli Zeitler: email@example.com
IMM Communications: firstname.lastname@example.org